1. Field of the Invention
The present invention relates to a communication device as well as a communication apparatus and a communication system that include the communication device.
2. Description of the Related Art
In a communication system, transfer vehicles transfer articles to and from stations, and in the case of transferring semiconductors for example, the transfer vehicles perform communication for transfer with station-side terminals in accordance with the SEMI standard E84 (called E84 hereinafter) protocol. A transfer vehicle stops at a position facing a station and performs communication, and it is unclear whether or not the station side is prepared for transfer until E84 communication is started. For this reason, there are cases where the transfer vehicle stops and determines through E84 communication that transfer cannot be performed, and then the transfer vehicle departs from the station without transferring articles. Accordingly, the transfer vehicle makes needless stops, and there are cases where congestion occurs due to blocking the traveling route.
One reason why this problems occurs is that the transfer vehicle side is not provided with a means for finding out the statuses of stations at a position away from the stations. Note that WO 2011/155040, which is related to E84 communication, proposes a technique in which a transfer vehicle starts E84 communication directly upstream of a station, without stopping. However, since multiple transfer vehicles are traveling in actuality, enabling the transfer vehicles to perform E84 communication at a position other than directly upstream of the station as in conventional technology requires exclusive control in which multiple transfer vehicles do not control the same station at the same time.